Most automotive vehicles include some form of supplemental restraint system, such as, for example, an inflatable airbag, that supplements the seatbelt system of the vehicle to enhance protection of a vehicle occupant during a load event (e.g., vehicle impact or collision). For example, a typical frontal impact causes the occupant (e.g., driver or passenger) to move forward toward a dashboard (or instrument panel), glove compartment (or glove box), or other vehicle compartment. Accordingly, the supplemental restraint system can include one or more airbags that are deployed in front of the vehicle occupant to substantially prevent the occupant from impacting the front compartment(s) of the vehicle.
One type of frontal airbag is a knee airbag that deploys in front of the lower legs and/or knees of the occupant to help prevent impact with lower portions of the vehicle compartments. Many knee airbags include a single internal chamber that spreads laterally upon deployment in order to evenly cover both legs of the occupant. However, such knee airbags typically do not account for load events that occur off-center or at an angle to a direction of motion of the vehicle (such as, e.g., an offset impact, a “small offset, rigid barrier” (SORB) impact, an angle impact, etc.) and therefore, cause the occupant to move laterally within the vehicle cabin, for example, towards a door or center console of the vehicle, in addition to moving forward. Further, many existing knee airbags do not account for other forms of uneven intrusion, or load distribution, on the knees and/or legs of the occupant during an impact, for example, due to an uneven engine compartment package in the vehicle cabin, a sweep of a lower portion of the instrument panel or glove box (e.g., in the area adjacent to the knees or legs of the occupant), or a difference in stiffness between the instrument panel, the glove box, the center console, or other vehicle compartment.
For example, one existing knee airbag has a non-symmetrical, single-chamber design comprising an enlarged, thicker portion at the end of the airbag that faces an outboard side of the vehicle, so as to limit both lateral and forward movement of the occupant during a load event. However, the frontal or main portion of the airbag has a uniform thickness and stiffness that does not account for uneven intrusions within the vehicle cabin that may affect the load distribution on at least a front side of the knees and/or legs, or an amount of energy that is expected to be absorbed at the different contact areas.
Other existing knee airbags have multi-chamber designs with uneven volumes, air pressures, or inflation timings to vary the coverage applied to different knees and/or areas of the legs. However, an overall shape, volume, and stiffness of each chamber in such knee airbags cannot be individually, or asymmetrically, tuned to account for, for example, a geometry of the various compartments within the vehicle cabin or an expected amount of energy to be absorbed upon occupant contact with the chamber.
Accordingly, there still exists a need for an improved knee airbag that can be asymmetrically configured according to uneven intrusions on the airbag, including vehicle cabin geometry, so as to provide an appropriate load distribution to each knee and/or leg of the vehicle occupant in various types of impacts (e.g., frontal impact, offset impact, angle impact, etc.).